For the first time in census history, there are more seniors than children living in Canada.

According to results from the 2016 census released Wednesday, there were 5.9 million people aged 65 and older in Canada – just slightly more than the country’s 5.8 million children under 14.

Statistics Canada attributes this, in part, to the post-war baby boom. As the first group of baby boomers turned 65 and entered their senior years, they had a disproportionate impact on Canadian demographics. Canada’s low fertility rates also contributed, as did the fact that Canadians are living longer than ever.

“The reason is basically that the population has been aging in Canada for a number of years now and the fertility level is fairly low, below replacement levels,” said Andre Lebel, a demographer with Statistics Canada.

Over the next 16 years, the rest of the baby boom will become senior citizens, he said, “That’s why we foresee that the proportion of seniors will get up to 23 per cent within the next 15 years.”

“This is actually the level that is seen in Japan right now. They have 25 per cent of their population being seniors. We will get there in 15 years in Canada.”

Canada won’t stand out among industrialized countries either, he said. “We know for a fact that all other G7 and all industrialized countries in the next 15 years will see more seniors in their population than children.”

Young Prairies, old coasts

The Prairie provinces have a younger population overall than the Canadian average. They also have more children under 14 than seniors over 65.

It’s the opposite story on the east coast.

While Alberta seniors only make up 12.3 per cent of the province’s population, one in five people in Atlantic Canada are over 65.

WATCH: Everything you need to know about the 2016 census

This is due to “low fertility, low immigration levels and migratory losses to other regions of Canada,” according to Statistics Canada. Of these, fertility levels are by far the most important factor, said Lebel, and people in the prairies and territories have more children than people in Atlantic Canada.

Parts of British Columbia aren’t that young either.

The province has a similar proportion of seniors as Atlantic Canada, but in parts of Vancouver Island, more than two in five people are over 65. Victoria has the lowest proportion of children among all Canadian municipalities, with only 13 per cent of people aged 14 and younger.

Young and urban

The proportion of people aged 15 to 64 was higher, at 67.8 per cent, in metropolitan areas than outside them, at 63.8 per cent.Calgary had the highest percentage of working-age people, followed by Vancouver.

“Large cities, like Montreal, Toronto and Vancouver do welcome a lot of immigrants,” said Lebel. “And also they have a lot of universities, so people going there to study, often from other areas of their provinces.”

Atlantic cities also buck the overall aging trend of their region. St. John’s had the third-highest proportion of working-age people, followed by Halifax.

WATCH: Small towns in Atlantic Canada are desperately looking for answers to a troubling demographic equation. Ross Lord reports.